Gold dredge



Patented Dec. 9, 1941 UNITED STATES PATENT OFFICE GOLD DREDGE John M. Nicol, Mill Valley, Calif. Application June 1, 1940, Serial No; 338,34?

Claims. 37-71) The present invention relates to a dredge of the floating type adapted for excavating gravel and separating therefrom free gold or other precious metals.

In the operation of dredges of this general type,

the machinery for separating the gold from the gravel is mounted on a pontoon floating either in a natural body of water or in an artificial pond. The gravel is excavated at the forward end of the pontoon, passed through the separating machinery and discharged at the rear end of the pontoon. In the larger sizes, dredges of this type are self-contained, i. e. the excavating machinery, usually comprising an endless chain bucket excavator, is mounted directly on the forward end of the pontoon and projects therefrom. In the smaller sizes, the excavating machinery is separately mounted on the bank of the pond, and usually comprises a bucket or drag line dredge or a power shovel, which dumps the excavated material into a hopper on the pontoon, from which it passes to and through the separating machinery. The latter construction necessitates moving two separate units as the excavation progresses.

The principal object of my present invention is to provide a self-contained dredge of the drag line type, which is suitable for ground that cannot be satisfactorily operated by the usual endless chain bucket dredge. lt is also adapted to small installations. The nature of my present invention provides the essential means of making the drag line type of dredge self-contained, which has never heretofore been done, in that the drag line bucket digs downwards and away from the pontoon and is enabled to return and deliver the load of excavated material directly on the pontoon. This object is achieved by the use of a drag line bucket excavator mounted directly on the forward end of the dredge and arranged in such a manner that the bucket excavates in a direction away from the dredge and then ele- Vates and brings back its load, and dumps it into a receiving hopper at the forward end of the dredge. By'this novel arrangement, the bottom of the pond is kept clear ahead of the dredge and sufficient depth of water is maintained to insure free floating of the dredge pontoon as it advances. The advantages of the drag line excavator are therefore made available to floating dredges without the necessity of using two separate units.

Another object of the invention is to provide .a bifurcated boom extending from the forward end of the dredge for carrying the drag line bucket, and means at the outer end of said boom for supporting it on the gravel beyond the line of excavation with a special type of spud when required. The use of a spud on the outer end of a drag line boom, which has never heretofore been done, has the following great advantages: it prevents undue leverage at maximum load, and in a large measure prevents surgence on the dredge pontoon, a very important factor in insuring good gold saving efficiency.

Another object of the invention is to provide an arrangement of gravel discharging means at the rear end of the pontoon which will deposit the boulders and larger particles of gravel at the bottom of the pond and will place the finer particles, sand and mud on top thereof. This arrangement of discharging the washed material, known in the art as re-soiling, leaves the land over which the dredge has passed in a suitable condition for agriculture, and is of great importance in preventing destructionby the dredging operation of usable agricultural land.

Still another object is to arrange the separating machinery on the pontoon on two decks one above the other, in order to reduce the length of the pontoon and the distance to which the discharging means must extend beyondits rear end.

Still further objects and advantages of the invention will become apparent from the following description, which should be read with the understanding that changes, within the scope of the claims hereto appended, may be made in the form, construction and arrangement of the several parts herein described, without depart-' ing from the spirit of the invention.

Reference will be made to the accompanying drawings in which Fig. 1 is a diagrammatic side elevation of my improved dredge.

Fig. 2 is a diagrammatic plan view of the same.

In the drawings, the reference numeral ll designates a pontoon floating upon a body of water, the surface of which is indicated at l2. From the forward end of the pontoon there extends a boom l3 comprising two horizontally spaced longitudinal members l4 connected together by a suitable cross member 15. The inner end of the boom 13 is hinged to the pontoon at IS in order to allow its outer end to be raised and lowered.

Av mast or gantry ll rises from the forward end of the pontoon, and suitable elevating cables l8 extend from the top of the gantry to the outer end of the boom l3. The specific arrangement of the elevating or supporting cables 18 and the means by which they are operated to raise lower the outer end of the boom l3, form no of the present invention, and are omitted the drawings.

The outer end of. the boom is provided with a spud 20, the foot of which rests upon the bank 2| of the pond, and furnishes independent and solid support for the boom I3 in order to prevent tipping or pitching of the pontoon during operation. The spud 20 is vertically slidable in guides 22 at the outer end of the boom I3, and any suitable means, herein indicated as a system of cables 23 and sheaves 24, is provided for raising and lowering the spud, or for raising and lowering the end of the boom on said spud when the lat ter is grounded on the bank.

and part from An excavating bucket 25 is moved and guided which pass between the by drag lines 26 and 21, longitudinal members of the boom l3, and are carried over sheaves 28 at the top of the gantry andthence down to hoisting mechanism 29 on the upper deck of the pontoon. The drag lines 26 run directly from the bucket 25 to the gantry sheave 28, whereas the drag line 21 runs from the. bucket 25 over a sheave 30 at the forward end of the boom, and thence to the gantry sheave 28. By proper operation of the drag lines 26 and 21, the bucket 25 can be lowered to the bottom of the pond at any point ahead of the forward end of the pontoon, then dragged upwardly and outwardly along the bottom to excavate the gravel in a direction away from the pontoon, and then elevated and swung rearwardly through the boom to a dumping position above the forward end of the pontoon. The specific construction of the bucket 25, and the dumping mechanism thereof, are features of common knowledge in the art, and are neither illustrated nor described herein.

The pontoon is provided with a lower deck 3| and an upper deck 32, suitably supported by stanchions 33. A receiving hopper 34 into which the bucket 25 dumps its load of gravel is positioned at the forward end of the pontoon, at the level of, or slightly above, the upper deck. The hopper 34 has a downwardly and rearwardly sloping bottom 35. Above said bottom is a downwardly and rearwardly sloping grizzly 36 consisting of longitudinal bars spaced apart a proper distance to catch the larger boulders, and to permit the smaller rocks and fine material to pass through. At the rear of the grizzly are two laterally directed chutes 31 extending outwardly beyond the sides of the pontoon down which the boulders roll and are dumped into the water. If desired, the boulder chutes 31 may be extended rearwardly along the sides of the pontoon to points near its rear end.

The bottom 35 of the receiving hopper terminates in a chute 38 which feeds the boulder free material into the forward end of a rotating drum 33, mounted between the upper and lower decks. The drum 39 has a forward section provided I with a tight shell 40 and suitable interior elevators, not shown, which constitutes a scrubber for tumbling and cleaning gravel and breaking up any cementitious material. The rear section I of the drum 39 is a perforated screen or trommel 4|, which separates the rocks from the finer portions of the gravel.

A chute 42 catches therocks and coarse matej rial which come out from the rear end of the trommel 4|, and conveys them rearwardly and dumps them fromthe rear end of the pontoon.

. known in the art. Its rear end is suspended by a The rear portion of the chute 42 is bifurcated as shown.

The finer material which passes through the trommel 4| is washed through sluices 43 containing riflies, not shown, in which the initial separation of gold takes place in a well known manner. From the sluices 43, the material passes over a suitable separator 44in which a further separation of the fines from the coarser material takes place. The coarser material from the separator 44 is discharged directly to a belt stacker 46 which carries it out between the bifurcated ends of the chute 42 and dumps it well beyond the rear end of the pontoon. The belt stacker 46 may be of any ordinary construction well cable 41'from masts 48 at the rear end of the pontoon.

The fines from the separator 44 are carried by a chute 49 to sand pumps 50 and lifted by said pumps through pipes 5| to an elevation above the upper deck and discharged into a system of final separators, which may be of any suitable type and form well known in the art, and which are capable of removing the fine gold from the sand and mud. As a preferred example of such a separating system, I have shown sluices 52 which feed throughtroughs 53 into rotary separators 54, the latter discharging the sand and mud into launders 55 extending rearwardly from the, pontoon beyond the end of the belt stacker 46. The launders' 55 are supported by cables 56 from the masts 48, and are preferably arranged so that they may be swung from side to side to distribute the discharged sand and mud.

It will be seen that, by providing the bifurcated boom l3, supported at its free end by the spud 20, I am able to use successfully the simple and inexpensive drag line bucket excavator, and to mount and operate the same on the pontoon itself, thus making a self-contained dredge. The novel arrangement of bifurcated boom, spud, and drag line excavator, permits the bucket to dig away from the pontoon, keeping the bottom of the pond clear for free floating and advance of the dredge, and to return the excavated material and dump it into the receiving means at the forward end of the dredge.

It will also be seen that my arrangement of separating apparatus on two decks permits selective discharge of waste material in such a manner that the boulders and larger gravel are discharged ahead of. and therefore lie beneath, the finer material, so that the land is left in a suitable condition for agriculture.

I claim:

1. A dredge adapted for operation in a pond comprising a pontoon, a mast rising therefrom, a boom extending from the forward end of the pontoon, means for supporting the outer end of said boom on the bank of the pond, gravel receiving" means on the pontoon at the forward end thereof, drag lines supported and guided by said mast and said boom, a digging bucket carried by said drag lines arranged to dig into the bank of the pond in a direction away from the forward end of the pontoon and to dump into said receiving means, and hoisting mechanism on the pontoon for operating said drag lines.

2. A dredge adapted for operation in a pond comprising a pontoon, a mast a boom extending from the forward end of said pontoon, guide means at the outer end of said boom, a vertically movable spud mounted in said guide means for supporting the outer end of rising therefrom,

said boom on the unexcavated ground, means for raising and lowering the outer end of said boom on said spud, means on the pontoon at the forward end thereof for receiving excavated material, drag lines supported and guided by said mast and said boom, a digging bucket carried by said drag lines arranged to dig into the bank of the pond in a direction away from the forward end of the pontoon and to dump into said receiving means, and hoisting mechanism on the pontoon for operating said drag lines.

3. In a floating dredge, a pontoon, a mast rising therefrom, a boom extending from the forward end of said pontoon, said boom having two laterally spaced longitudinal members, means for supporting the outer end of said boom on unexcavated ground, means on the pontoon for receiving excavate-d material, drag lines supported and guided by said mast and said boom, a digging bucket carried by said drag lines and arranged to dig in a direction away from the forward end of the pontoon, said bucket operating through the space between the two members of said boom and dumping its load into said receiving means, and hoisting mechanism on the pontoon for operating said drag lines.

4. In a floating dredge, a pontoon, a mast rising therefrom, a boom extending from the forward end of said pontoon, said boom having two laterally spaced longitudinal members, means for supporting the outer end of said boom, means on the pontoon for receiving excavated material, a sheave at the outer end of said boom, sheaves on said mast, hoisting mechanism on the pontoon, an excavating bucket having its digging edge drected away from the pontoon, a drag line extending from said bucket forwardly over the sheave at the outer end of said boom and thence over a sheave on said mast to said hoisting mechanism, a second drag line extending from said bucket between the two member of said boom over a sheave on the mast to said hoisting mechanism, said drag lines operating said bucket to excavate in a direction away from the forward end of the pontoon and to elevate its load between the members of said boom and dump it into said receiving means.

5. In a floating dredge, a pontoon, a mast rising therefrom, a boom extending from the forward end thereof, aid boom having two laterally spaced longitudinal members, means at the outer end of said boom for supporting it on unexcavated ground, a hopper for receiving excavated material positioned at the forward end of the pontoon, a bucket arranged to dig in a direction away from the pontoon and to dump in a direction toward said pontoon, hoisting means on the pontoon, and drag lines extending between said hoisting means and said bucket, said hoisting means and said drag lines being arranged to cause said bucket to dig away from the pontoon and to return through the space between the longitudinal members of said boom and to dump its load of excavated material rearwardly into said hopper.

JOHN M. NICOL. 

